Alloy,fusion overlay and process

ABSTRACT

IN MAKING PUMP PARTS SUCH AS IMPELLERS, SHAFTS, BEARINGS AND THE LIKE, A SUITABLE BACKING SUCH AS STEEL IS COATED WITH A FUSED OVERLAY OF AN ALLOY OF TIN, BISMUTH, SILICON, BORON, OPTIONALLY CHROMIUM AND THE BALANCE NICKEL. THIS GIVES TO THE PARTS COATED BEARING PROPERTIES AND CORROSION RESISTANCE WITHOUT THE DANGER OF EXCESSIVE POROSITY. THE COATING IS DEPOSITED AND FUSED BY CONVENTIONAL METHODS.

June 20, 1972 J. F. LYNCH ETAL ALLOY, FUSION OVERLAY AND PROCESS 3 Sheets-Sheet 1 Filed Jan. 12, 1971 YSON SCOTT J. PAOLETT\ WW JOHN F WILLIAM BE ALFRED ATTORNEY! June 20, 1972 J. F. LYNCH ETAL ALLOY, FUSION OVERLAY AND PROCESS s Sheets-Shet 2 Filed Jan. 12, 1971 WILUAM BRYSON SCOTT ALFRED J. PAOLETTI 9V W,

June 20, 1972 Filed Jan. 12, 1971 J. F. LYNCH ETA!- ALLOY, FUSION OVERLAY AND PROCESS AL BY 2 44a,

5 Sheets-Sheet 5 United States Patent 3,671,207 ALLOY, FUSION OVERLAY AND PROCESS- John F. Lynch, Chester, Pa., and William Bryson Scott, Cherry Hill, and Alfred J. Paoletti, Willingboro, N.J., assignors to Marco Development Co., Inc., New Castle,

Del.

Filed Jan. 12, 1971, Ser. No. 105,816 Int. Cl. C22c 13/00; B32b /00 US. Cl. 29196.6 9 Claims ABSTRACT OF THE DISCLOSURE DISCLOSURE OF INVENTION The present invention relates to an alloy, a pump part coated with a fused overlay of the alloy and a process of making a pump part by depositing and fusing.

A further purpose is to produce an alloy having the following composition by weight:

Percent Tin 4-8 Bismuth Silicon 25 Boron 2-5 Chromium 1 I 0-17 Nickel Balance 1 Preferably 5-17 A further purpose is to deposit the overlay on parts which have previously been subjected to excessive wear in pump impellers, shafts, bearings, stator plates, housings, extrusion screws and liners which have previously been subjected to excessive wear in service.

A further purpose is to use fusion spraying, as for example, plasma spraying, or spray and fusion overlaying, or welding overlay to deposit the coating.

A further purpose is to produce an overlay alloy which has adequate hardness and resistance against wear, good anti-galling properties and excellent properties in resisting corrosion.

Further purposes appear in the specification and in the claims. 7

FIG. 1 is a diagrammatic longitudinal section of a ma spray gun used in the invention.

FIG. 2 is a chemical reactor pump having impeller plates interposed by stator plates shown in axial section.

FIG. 3 is a side elevation of one impeller plate to which the invention has been applied.

plas- FIG. 4 is a section of FIG. 3 on the line 44 show- Percent Nickel 50-70 Chromium 10-15 Molybdenum 2-3 Tin 2.5-5

Patented June 20, 1972 f ce ' Percent Bismuth 24 Silicon 0.25-0.75 Manganese 0.50-1.5 Iron Balance This alloy used in the form of castings has given a great deal of trouble because of the difficulty in making sound castings on account of the vaporization of tin and hismuth, and the excessive problem of dross. Castings commonly are made under conditions of frothing, foaming, and wildness of metal and presence of gas cavities.

In order to reduce the difficulty in production, and at the same time to eifectively protect against corrosion and impart anti-galling properties to pump parts, such as rotor plates, stator plates, shafts, extrusion screws, liners, housings and bearings, we have discovered an alloy which can be deposited as a coating on the fabricated or cast steel plates or other backing metal and which is free from difliculty with porosity, while at the same time producingadequate anti-galling properties and protection against corrosion.

The alloy of the invention has the following composition by weight:

In addition, it may have as impurities traces of iron, cobalt, and copper.

The tin is slightly soluble in the nickel and acts as a carrier for the bismuth. The bismuth imparts anti-galling properties along with the tin. Silicon and boron cooperate in producing a hard alloy, and also contribute importantly in deoxidizing and fluxing during fusion of the coating.

Chromium is not essential but contributes importantly to the corrosion resistance and the hardness. Thus, the alloy made without chromium has a hardness of R 18 while the alloy'made with substantial chromium increases in hardness to R 62. The preferred alloy has 5-17% chromium.

The nickel contributes corrosion resistance and is especially good when used with chromium.

While the alloy may be applied by any overlaying technique, such as welding overlay, it is preferably applied by fusion spraying, or spray and fusion overlaying, with a plasma torch, the alloying ingredients being introduced as powder.

Relatively thin overlay surfaces may be produced by the invention, for example as thin as 0.005 inch or the overlay may be quite thick, for example inch, although an overlay of thickness of V inch is a more practical limit.

The plasma torch may be of the type which employs a transferred or non-transferred plasma arc.

, FIG. 1 conventionally shows a plasma gun consisting of an axial electrode 20 connected to an electric terminal 21, insulated by a nylon sleeve 22 and cooled by a water jacket 23. An arc is established by the electrode 20 and a water cooled tubular electrode 24. A gas is introduced at 25, such as argon, to form the plasma 26 into which powder is introduced through a side port 27. The powder may have a size between 200 and 250 mesh per linear inch although coarser powder may be used and finer powder is preferred.

FIG. 2 shows in axial section a chemical reactor pump consisting of a housing 40, stator plates 41, impeller plates 42 on a suitable shaft 43 having a hexagonal portion 44 engaging the impeller plates. Inlet is at 45, and

J K 3,671,207 p the outlet is at 46. The details are shown more fully in Lynch et al., US. Pat. 3,356,461, granted Dec. 5, 1967 for Condensate Cone for Continuous Chemical Reactors.

In FIGS. 3 and 4 an impeller plate 42' is shown having vanes 50 extending laterally to the edge of the impeller plate, curving in one direction on one side of the impeller plate and in another direction on the other side of the impeller plate to pump the fluid radially out at one'side and radially in at the other side. There is a hub at 51.

The impeller has a steel backing 52, suitably a steel casting, and it has a surface layer 53 on the wear parts which is deposited by fusion spraying, and machined down to size.

In FIG. 5 an impeller plate 42 has a backing, suitably a steel casting 52, and has spiral vanes 50 which spiral in opposite directions on opposite sides of the impeller plate. The vanes and other wear parts are machined below the dimension required and then a fusion spray coating 53 is applied according to the invention and machined down to proper size.

Example 1 An alloy having the following composition by weight is sprayed and fused by a plasma gun on the wear sur faces of a steel impeller:

Percent Tin Y 6 Bismuth A 6 Silicon t. 3.5 Boron 3.5 Chromium 11 Balance Nickel The layer is built up to 0.020 inch and then machined down to a thickness of 0.015 inch at which-the impeller is of proper size. a

The anti-galling and corrosion resistant properties are superior to the alloy of Thomas and Williams US. Pat. 2,743,176. The hardness is R 62, and the yield strength and tensile strength are correspondingly good.

- Example 2 p The overlay alloy of Example 1 is applied by electric arc welding overlay, using a consumable electrode of nickel, and adding the other ingredients in a flux core under an atmosphere of argon. The results are effectively the same as those obtained in Example'l.

Example 3 p The procedure of Example 1 is carried out on a pump impeller in which the overlay has the following composition by weight:

a Percent Tin 1 6 Bismuth 6 Silicon 3.5 Boron 3.5 Nickel Balance The composition much softer than that of Example 1, having a hardness of R 18. Other than the fact of its being less hard, however, it adequately functions from the standpoint of anti-galling properties and corrosion rewill doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the process, alloy and structure shown, and we, therefore, claim all such insofar as they fall within the reasonable spirit and scope of o'ur claims.

Having thus described my invention what we claim as new and desire to secure by Letters Patent is:

1. An .alloy essentially consisting of the following com- Percent Tin 4.3 Bismuth 4-8 Silicon 2-5 Boron 2-5 Chromium 0-17 Nickel Balance 2. An alloy of claim 1, which essentially consists of the following composition by weight:

Percent Tin 4.8 Bismuth 4-8 Silicon 2-5 Boron 2-5 Nickel Balance '3. An alloy of claim 1, which essentially consists of the following composition by weight:

Percent Tin 4.s Bismuth 4. 8 Silicon 2-5 Boron 2-5 Chromium 5-17 Nickel Balance 4. A pump having a steel base metal and fused overlay of an alloy having the following composition by weight:

. Percent Tin 4-8 Bismuth 4-8 Silicon 2 -5 Boron '2 5 Chromium 0-17 Nickel Balance 5. A pump part of claim 4, in which the fused overlay has the following composition by weight:

I Percent Tin 4-8 Bismuth 4- Silicon 2-5 Boron Y 2-5 Nickel Balance 6. A pump part of claim 4, in which the fused overlay has the following composition by weight:

n A method of forming a pump part which comprises depositing and fusing on a steel backing an alloy havin the following composition by weight:

Percent 5 8. A method of claim 7, in which the alloy has the following composition by weight:

9. A method of claim 7, in which the alloy has the following composition by weight:

Percent Tin 4-8 Bismuth 4-8 Silicon 2 5 Boron 2-5 Chromium 5-17 Nickel Balance References Cited UNITED STATES PATENTS 5/1938 Matsuyama 75-171 2/1959 Tour 75-471 3/1959 Millis 29-4966 5/ 196 0 Shepard 75-171 4/ 1969 Cape 75171 10 HYLAND BIZOT, Primary Examiner US. Cl. X.R. 

